In a W-CDMA (Wideband Code Division Multiple Access) system, immediately after turning on the power, before entering soft handover, or during intermittent reception mode for standby, a mobile station needs to detect the cell with the smallest pass loss (the cell with the second smallest pass loss upon entering soft handover). This process is referred to as cell search, as it involves searching for cells required for establishing a radio link.
Typically, synchronization of spreading codes requires correlation detection at each timing accounting for the length (the number of chips) of every spreading code which needs to be searched, and then requires the detection of synchronization points. In the downlink, the number of scrambling codes is determined as a sufficiently large value, 512, to enable flexible scrambling code assignment. Accordingly, during initial cell search, the mobile station needs to sequentially perform the search on 512 types of scrambling codes, which is usually an extremely time-consuming process. With this in mind, a three-step cell search method has been proposed to enable fast cell search in an inter-BS (base station) asynchronous system (see “W-CDMA MOBILE COMMUNICATIONS SYSTEM” edited by Keiji Tachikawa, Japan, Mar. 15, 2002, pages 35-36).